Chiral purity pharmaceutical

Molecules which exhibit optical activity are molecules which have a handedness in their structure. They are chiral . Chemists often have reasons to obtain chemical pure aliquots of particular molecules. Since the chirality of molecules can influence biological effect in pharmaceuticals, the chiral purity of a drug substance can pose a challenge both in terms of obtaining the molecules and in assaying the chiral purity by instrumental methods. While diastereomers can have different physical properties including solubility, enantiomers have the same physical properties and the same chemical composition. How then to separate optically active molecules ... 

In Table 1, the typical validation parameters required for the different types of analytical procedures are listed. For all these analytical procedures CE might be an appropriate analytical technique. In fact numerous validated CE methods for pharmaceutical analysis have been described in literature during the last decade.In Table 2, an overview is listed of the ICH validation parameters included in several reported CE validation studies. Since chiral purity determination is an important application area of CE methods, this test is listed separately as a specific analytical procedure. In addition, the determination of drug counterions has been included as a separate application. This overview illustrates that in general the required validation parameters are addressed in reported CE validation studies. It should be noted, however, that the validation parameters included in Table 2 are not necessarily evaluated exactly according ICH requirements in the reported references. Many pharmaceutical companies apply a phase-related validation approach in which the depth of validation depends on the clinical phase of development of the product involved. 

CE is an important separation technique within the field of pharmaceutical analysis. CE may be an attractive choice as analytical procedure for identification, assay, or (chiral) purity determination. In addition, CE may provide distinct advantages over existing pharmacopoeial... 

Much of the knowledge needed for manufacturing a pharmaceutical is related to the last step in the process, including understanding the bulk active ingredient, its impurity profile, chiral purity, and crystal form. To cut down the entire scale-... 

Numerous methods are required to characterize drug substances and drug products (Chapter 10). Specifications may include description identification assay (of composite sample) tests for organic synthetic process impurities, inorganic impurities, degradation products, residual solvents, and container extractables tests of various physicochemical properties, chiral purity, water content, content uniformity, and antioxidant and antimicrobial preservative content microbial tests dissolution/disintegration tests hardness/friability tests and tests for particle size and polymorphic form. Some of these tests may be precluded, or additional tests may be added as dictated by the chemistry of the pharmaceutical or the dosage form. 

Property data from pharmaceutical prohling is not exclusively for optimizing PK. It can be considered as part of the multivariate ensemble of data (e.g., MW, chirality, purity, IC50, LD50) that is available to research teams for application to any drug-discovery experiment. 

One of the most important and challenging areas in the analysis of pharmaceuticals is the determination of chiral purity. It is therefore highly appropriate that a chapter is devoted to this area. The importance of chiral analysis is described, together with the development of techniques across the separation sciences and beyond. 

Menthol is the chief flavoring agent in mint and peppermint and is used in candy, tobacco, oral care items, pharmaceuticals, and various other products. Takasago developed the synthesis of (-)-menthol (in the 1980s) from myrcene, which is converted to diethylgeranylamine by the lithium-catalyzed addition of dieth-ylamine. This is then catalytically isomerized to the chiral 3R-citronella enamine with 96-99% enantiomeric excess. Hydrolysis of this intermediate gave 3R-(+)-citronella a higher chiral purity than citronella from citronella oil. This is the second major corn-... 

Figure 50 shows the potential fo packed-column SFC for an efficient and fast control of the chiral purity of pharmaceuticals. Because of the excellent solubility of lipids in supercritical carbon dioxide, SFC in combination with the universal FID detector is a very helpful tool in lipid analysis. 

Sharpless asymmetric epoxidation (SAE) is the epoxidation of allylic alcohols into asymmetric epoxides in high chiral purity (high enantioselectiv-ity). Transition metal catalyst Ti(OPr ) with chiral additive, diethyl tartarate (DET), generates chiral catalyst (Scheme 9.40) which is responsible for the enantioselective outcome, while, tert-butyl hydroperoxide (TBHP) serves as an oxidant. Although, this eatalytic system holds disadvantage of low turnover number (TON) with potential safety coneems for using concentrated solutions of peroxides, the reaction has nevertheless been extensively used in pharmaceutical industry [76]. 

The second section of the book comprises Chapter 10 through 15, covering a considerable spectrum of practical TLC enantioseparations within a variety of important compound classes. Chapter 10 deals in a general way with the chirality of pharmaceutical product racemates, viewing them both from a perspective of their use as medicines and also as chiral selectors in the TLC separation procedures. This chapter also provides important information on the methods of controlling the racemate purity. 

The first part of the book examines the fundamental principles of chirality and TLC. It describes the necessary materials, laboratory equipment, procedures, and strategies for the separation, quantification, isolation, and analysis of chiral compounds. The second part evaluates the reaUworld enantioseparations and densitometric analyses. Emphasizing pharmaceutical applications, the book examines the chiral separation mechanisms and methods for analyzing the chiral purity of diastereoisomers, amino acids, beta-blockers, and NSAIDS. Topics also include commercial stationary phases and chiral modifiers of mobile phases. 

Because process mixtures are complex, specialized detectors may substitute for separation efficiency. One specialized detector is the array amperometric detector, which allows selective detection of electrochemically active compounds.23 Electrochemical array detectors are discussed in greater detail in Chapter 5. Many pharmaceutical compounds are chiral, so a detector capable of determining optical purity would be extremely useful in monitoring synthetic reactions. A double-beam circular dichroism detector using a laser as the source was used for the selective detection of chiral cobalt compounds.24 The double-beam, single-source construction reduces the limitations of flicker noise. Chemiluminescence of an ozonized mixture was used as the principle for a sulfur-selective detector used to analyze pesticides, proteins, and blood thiols from rat plasma.25 Chemiluminescence using bis (2,4, 6-trichlorophenyl) oxalate was used for the selective detection of catalytically reduced nitrated polycyclic aromatic hydrocarbons from diesel exhaust.26... 

Enantiometrically pure alcohols are important and valuable intermediates in the synthesis of pharmaceuticals and other fine chemicals. A variety of synthetic methods have been developed to obtain optically pure alcohols. Among these methods, a straightforward approach is the reduction of prochiral ketones to chiral alcohols. In this context, varieties of chiral metal complexes have been developed as catalysts in asymmetric ketone reductions [ 1-3]. However, in many cases, difficulties remain in the process operation, and in obtaining sufficient enantiomeric purity and productivity [2,3]. In addition, residual metal in the products originating from the metal catalyst presents another challenge because of the ever more stringent regulatory restrictions on the level of metals allowed in pharmaceutical products [4]. An alternative to the chemical asymmetric reduction processes is biocatalytic transformation, which offers... 

Capillary electrophoresis (CE) has become a valuable technique in the analytical toolbox for pharmaceutical analysts. CE methods have been successfully applied for identification, assay, purity determination, and chiral separation. ICH guidelines should be followed in meeting regulatory approval if CE methods are used in a registration dossier. Here, the validation parameters required for different analytical procedures are described and a comprehensive overview of CE validation studies presented in literature is given. 

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